Iridotomy to slow progression of visual field loss in angle closure glaucoma (Review)

Methodological quality of the review: High confidence

Authors: Le JT, Rouse B, Gazzard G

Region: Asia

Sector: Angle-closure glaucoma

Sub-sector: Treatment

Equity focus: None specified

Review type: Other review

Quantitative synthesis method: Narrative synthesis

Qualitative synthesis method: Not applicable

Background:

Primary angle-closure glaucoma (PACG) is a type of glaucoma associated with a physically obstructed anterior chamber angle. Obstruction of the anterior chamber angle blocks drainage of fluids (aqueous humour) within the eye and may raise intraocular pressure (IOP). Elevated IOP is associated with glaucomatous optic nerve damage and visual field loss. Laser peripheral iridotomy (often just called ‘iridotomy’) is a procedure to eliminate pupillary block by allowing aqueous humour to pass directly from the posterior to anterior chamber through use of a laser to create a hole in the iris. It is commonly used to treat patients with PACG, patients with primary angle closure (narrow angles and no signs of glaucomatous optic neuropathy), and patients who are primary angle-closure suspects (patients with reversible obstruction). The effectiveness of iridotomy on slowing progression of visual field loss, however, is uncertain.

Objectives:

To assess the effects of iridotomy compared with no iridotomy for PACG, primary angle closure, and primary angle-closure suspects.

Main findings:

The authors identified two trials (2,502 eyes of 1,251 participants) that compared iridotomy to no iridotomy. Both trials recruited primary angle suspects from Asia and randomized one eye of each participant to iridotomy and the other to no iridotomy. Because the full trial reports were not available for both trials at the time of writing, no data was available to the authors to assess the effectiveness of iridotomy on slowing progression of visual field loss, change in IOP, need for additional surgeries, number of medications needed to control IOP, mean change in best-corrected visual acuity, and quality of life. Based on currently reported data, the authors note that one trial showed evidence that iridotomy increases angle width at 18 months (by 12.70°, 95% confidence interval (CI) 12.06° to 13.34°, involving 1,550 eyes, moderate-certainty evidence) and may be associated with IOP spikes at one hour after treatment (risk ratio 24.00 (95% CI 7.60 to 75.83), involving 1,468 eyes, low-certainty evidence). The risk of bias of the two studies was overall unclear due to lack of availability of a full trial report.

The authors concluded “The available studies that directly compared iridotomy to no iridotomy have not yet published full trial reports. At present, we cannot draw reliable conclusions based on randomized controlled trials as to whether iridotomy slows progression of visual field loss at one year compared to no iridotomy. Full publication of the results from the studies may clarify the benefits of iridotomy.”

Methodology: 

The inclusion criteria consisted of randomized or quasi-randomized controlled trials that compared iridotomy to no iridotomy in primary angle-closure suspects, patients with primary angle closure, or patients with primary angle-closure glaucoma in one or both eyes. Primary outcome measure included the proportion of participants with any progression of visual field loss at one year.

The authors searched the Cochrane Central Register of Controlled Trials (CENTRAL; 2017, Issue 9) which contains the Cochrane Eyes and Vision Trials Register; MEDLINE Ovid; Embase Ovid; PubMed; LILACS; ClinicalTrials.gov; and the ICTRP. The date of the search was 18 October 2017. In addition, the authors also searched references of included studies for information about further trials. No language or publication year restrictions were applied to searches.

Two authors independently screened studies for inclusion, extracted data and assessed risk of bias of included studies. Data analysis consisted of a narrative synthesis.

Applicability/external validity:

The authors did not draw reliable conclusions based on the studies included in the review.

Geographic focus: Both studies included were conducted in Asia.

Summary of quality assessment:

Overall, high confidence was attributed to this review. The authors used appropriate and rigorous methods to conduct the review. Although the authors did not find enough evidence in response to their research question, no strong conclusions were drawn.